This invention relates to an engine and lubricating oil with superior anti-wear properties which reduces air pollution by prolonging automobile catalytic converter life. More particularly, this invention relates to an anti-wear engine and lubricating oil which includes benzotriazole or the reaction products of benzotriazole with a stream comprising formaldehyde and an aliphatic amine, a sulfur-containing compound, and a metallic component.
Considerable work has been done with lubricating oils, mineral and synthetic, to enhance their anti-wear properties by modifying them with suitable additives. The use of lubricant anti-wear additives containing phosphorus has been well documented and widely implemented commercially. These additives include acid phosphates, phosphites, phosphonates, phosphate esters, metallic dithiophosphates, and the like.
Of the commercially successful phosphorus-containing lubricant anti-wear additives, zinc dialkyldithiophosphate (ZDDP) has been among the most commonly used. It is generally considered that ZDDP functions by forming a metal protective film of sulfide and phosphate decomposition products in boundary contact with the metal surfaces, thereby providing wear protection. In addition to anti-wear properties, ZDDP can also provide anti-oxidant capabilities.
While phosphorus-containing anti-wear additives do enhance engine and lubricating oil anti-wear performance, they also can contribute to reduced environmental air quality by adversely affecting automobile emissions systems. Automobile emissions systems generally comprising catalytic converters were developed to address air quality concerns and comply with legislation controlling vehicular emissions. Catalytic converters generally include precious metal oxidation catalysts and operate to facilitate the combustion of fuel to carbon dioxide and water while minimizing the products of incomplete combustion.
Catalytic converter performance generally deteriorates over time and often occurs as a consequence of chemical poisoning and physical deterioration. Lead and lubricant derived phosphorus, mainly from phosphorus anti-wear additives, have been identified as the primary catalyst poisons.
Phosphorus-containing lubricating oils can reach the automobile emissions systems in several ways. Oil can reach the combustion chamber through inlet valve guide leakage, turbocharger compressor seal leakage, and bypassing of the piston rings. Once combustion takes place, phosphorus-containing components are carried with the combustion flue gas to the emissions system where the phosphorus component can poison the catalytic converter catalyst.
While lead contamination will be substantially reduced with the complete phase out of lead from gasoline, phosphorus anti-wear additives are not being phased out of engine and lubricating oils. Phosphorus levels have been minimized to balance automobile manufacturer anti-wear requirements with catalytic converter life, but still are present due to lack of an adequate substitute for phosphorus-containing anti-wear additives.
Thus, a need exists to provide an engine and lubricating oil that provides superior anti-wear properties, consistent with the requirements of modern high performance engines, while not damaging emissions systems. While there exists a great need for such a composition, the art has been devoid of teachings and solutions, and automobile manufacturers and lubricating oil suppliers have continued with use of phosphorus-containing lubricating oils. This need may escalate if automakers are required to increase their emissions systems warranty period.
Benzotriazole and alkylbenzotriazole have been used commercially as corrosion and discoloration inhibitors for copper and copper alloys. In particular, benzotriazole is widely used in antifreeze, brake fluids, anticorrosion oils, electrical wires, copper products, coatings, photographic waxes, and cleaners. Various patents teach the use of benzotriazole compounds in industrial and gear oils.
British Patent No. GB 2,071,139 discloses an anti-staining compound including benzotriazole mixed directly with an aliphatic amine and a sulfurized aliphatic or alicyclic olefinic component for use in industrial and gear oils. The benzotriazole and aliphatic amine forms an organic salt that primarily minimizes additive side effects such as the staining of copper parts.
While benzotriazole and alkylbenzotriazole have found numerous commercial uses, their solubility characteristics limit these materials from other uses. Benzotriazole and alkylbenzotriazole are quite soluble in polar solvents such as methyl alcohol, acetone, and ethylene glycol, but only slightly soluble in benzene, toluene, xylene, and lubricating oil base stocks. The combination of benzotriazole or alkylbenzotriazole with an aliphatic amine alone, as described in British Patent No. GB 2,071,139, can produce an organic salt with limited solubility in lubricating oil base stocks. Benzotriazole and alkylbenzotriazole-containing organic salts, when alone, can "drop out" of conventional lubricating oil base stocks and are not widely used commercially.
Other patents teach methods to improve the solubility of benzotriazole or alkylbenzotriazole in engine and lubricating oils by creating a benzotriazole or alkylbenzotriazole structure that is non-ionic.
British Patent No. GB 1,061,904 discloses a compound made from the Mannich reaction of benzotriazole or alkylbenzotriazole, formaldehyde, and dialkylamines. The Mannich reaction compound exhibits improved solubility in lubricating oil base stocks and additional metal passivation properties.
Japanese Patent No. SHO 60 [1985]-194087 discloses a compound made from the Mannich reaction of benzotriazole or alkylbenzotriazole, an aldehyde, and a primary or secondary amine. The compound exhibits improved solubility in lubricating oil base stocks and additional properties for prevention of corrosion and the discoloration of metals.
It is therefore an object of the present invention to provide an engine and lubricating oil with superior anti-wear properties.
It is another object of the present invention to provide an engine and lubricating oil with high solubility in lubricating oil base stock.
It is yet another object of the present invention to provide an engine and lubricating oil that does not require a phosphorus-containing anti-wear additive.